Bug Description

In order to allow a smooth fallback from Unity 3D to 2D within the same session when lack of hardware/drivers support requires it, Metacity needs to be launched with the right options:
- capture before unmap activated
- compositing activated
- advanced compositing effects deactivated

This configuration of metacity should not be persistent and discarded as soon as the session exits (as to not impact for example the GNOME 2 session). Because of that it cannot be done through GConf/DConf and we should implement them as command line switches.

A new simpler, more generic solution was thought by Didier: adding a command line option to metacity where one could pass a file containing a set of GConf key/value pairs that override the current ones.